092 EDWARD PHELPS ALLIS, JR. 
the hyomandibula of the Batoidei is the pharyngeal element of 
its arch. The mouth and its bounding cartilages are, in the Ba- 
toidei, relatively transverse in position, and if this is not‘a primi- 
tive condition, it has been brought about by a shifting forward 
of the point of articulation, on either side of the head, of the 
cartilages of\the upper and lower jaws, instead of by a shifting 
backward of the dorsal and ventral ends of those cartilages. The 
epal and ceratal elements of the branchial arches were not dis- 
turbed by this shifting, and retained their oblique position relative 
to the axis of the body, and, as the hyobranchial visceral cleft 
did not undergo an expansion proportional to the increased dis- 
tance between the articular joints at the middle of the lengths of 
the first branchial and mandibular cartilaginous arches, the 
epihyal and ceratohyal, held in supporting relations to the 
anterior wall of the hyobranchial cleft, were pulled away from the 
mandibular cartilages. The pharyngohyal was notso held in 
place, for the pharyngeal elements of the branchialarches are never 
found in supporting relations either to the branchiae or the dia- 
phragms of the related clefts. Furthermore, the dorsal ends of the 
-hyal and branchial arches were apparently not pushed as far 
posteriorly in the Batoidei as in the Selachii, possibly because 
of the less pronounced cranial floxure in embryos of these 
fishes, and the thrust of the developing auditory capsule 
on the dorsal end of the pharyngohyal was lateral instead of 
posterior. This clement of the hyal arch was accordingly in posi- 
tion to be utilized for the purpose of giving the hyostylic sup- 
port to the mandibular cartilages that, in the Selachii, is given 
by the epihyal, and, as it was gradually pushed downward across 
the dorsal end of the epihyal, the latter element seemed to shift 
upward along its posterior edge in exactly the manner that Ge- 
genbaur (’72, p. 175) assumes for these very cartilages, consid- 
ered by him to be the epi-pharyngohyal and ceratohyal respec- 
tively. The pharyngohyal still retained its primary ligamentous 
attachments both with the epihyal and the epibranchial of the 
first branchial arch, through the interhyal and dorsal interarcual 
ligaments, and the conditions actually found in the adult Raia 
arose. The fact that it is a pharyngeal element and not an epal 
